1. Field of the Invention
The invention relates to a method and system for electronically controlling various operational parameters such as revolutions per minute (RPM), ignition spark timing, cylinder timing and gear shifting of an internal combustion engine. Specifically, the present invention allows such control via an interface that has an easy to read, word based menu system and method for easily changing related engine operational parameters.
2. Description of the Related Art
Conventional, mechanical methods of controlling engine parameters have been employed to govern the maximum revolutions per minute (RPM) the crankshaft of an engine rotates, set ignition spark timing and to control gear shifting.
In the past, revolutions per minute that the crankshaft rotates were limited by controlling the amount of fuel delivered for consumption. Modern, spark internal combustion engines typically utilize the ignition system to control RPM of the engine. Once the engine has reached the maximum RPM allowed, the ignition system will cut the electrical impulse to the spark plug, thereby preventing the spark plug from firing in the cylinder and consumption of fuel. Various methods have been employed to sequentially or randomly interrupt the firing order of the spark plugs. Adjustable RPM limiters typically utilize dial or resistor-type chips on the ignition box itself to set the maximum RPM allowed during operation. More complex RPM limiters allow for more than one RPM limit to be set for controlling RPM during various conditions or stages of operation. Once the maximum RPM of the first set dial or chip is reached, the engine is allowed to reach the next maximum RPM set by the next dial or chip and so on. One problem associate with these types of RPM limiters is that the adjustable dials are typically small and difficult to change in order to prevent the dial from rotating due to engine and chassis vibration. Furthermore, systems that utilize resistor chips are limited by what chips the user has and both systems are limited by the predetermined increments of the dials or the chips.
To increase performance and accuracy of timing in high revolutions per minute engines, electronic ignition systems were developed. As RPM increase, the timing cycles for delivering a spark to the cylinder becomes very compressed and further rotating parts, crank and camshaft, may bend under stress, thereby adding inaccuracies in conventional, mechanical timing systems. Electronic ignition systems overcome these mechanical inaccuracies by typically triggering the spark timing off of the flywheel or balancer on the crankshaft or the camshaft, thereby eliminating the need to mechanically adjust the timing at the camshaft and distributer.
For peak efficiency, the fuel must be ignited in the cylinder on the up stroke of the piston as the fuel mixture is under pressure to give the flame created by the spark time to travel across the cylinder and ignite the fuel mixture. For example, a spark timed to arrive at X degrees advance, before top dead center (TDC) of the piston, may actually spark many degrees before or after the set timing. Improper timing or inaccurate sparking may cause detonation in which the fuel ignites while the piston is at the early phase of the upward travel, pre-ignition, or later in the downward stroke which may damage the valve train assembly, piston, connect rod or in the extreme, the crankshaft.
Typically electronic ignition systems ramp up to a set degree of ignition timing as RPM increase. For example, with ignition timing set at 30 degrees advance, the actual ignition timing may begin from start up (0 RPM) at 10 degrees advance and linearly increase until the timing reaches 30 degrees advance at thousands of RPM later. One problem associated with electronic ignition timing systems, is the inability to set degrees ignition timing as a function of RPM or the ignition system may only allow changing slope of the linear ramp up timing, thereby preventing the engine from operating at peak efficiency or maximum power. Furthermore, these systems do not allow the changing of the ignition timing as a function of an event such as a gear shift.
Sudden changes in cylinder pressure due to the boost of a turbo charger, the injection of nitrous oxide into the fuel mixture, gear shifts or the combination thereof, present another problem for ignition timing. As cylinder pressure changes, the optimum ignition timing point may also change. Electronic ignitions systems have been developed to monitor cylinder or inlet manifold pressure and compensate for these changes, but are limited by the sampling rates of the electronics used and typically do not let the user input timing adjustments. Furthermore, in high performance applications, the timing adjustments cannot be made quickly to compensate for the rapid changing conditions.
To achieve peak engine performance in a racing application, the racer or crew chief may alter engine components and settings to find the optimum combination. Ignition timing is one such setting that must be optimized for each engine combination. The racer often finds the optimum ignition timing setting by adjusting the timing and making a run with the racecar to determine its effect. This process cannot only be time consuming, but also tedious due the physical requirements of manually changing the ignition timing.
Furthermore, varying weather conditions will also affect the performance of these types of engines. Any change in temperature, barometric pressure, humidity or combination thereof will affect the performance characteristics of the engine. Ignition timing is one parameter the racer may change to compensate for these changes in weather conditions.
Also, the racer may alter ignition timing to control the performance of the racecar. For example, in some drag racing applications were the race is run on an ET (elapsed time) index, the racer may desire to slow the ET of the racecar using ignition timing. By retarding the ignition timing, the racer can, in effect, de-tune the engine and elongate the elapsed time of the run. Thus, it is desirable to have an ignition timing system capable of allowing the user to pre-select timing changes as a function of RPM or events.
Another physical limitation of mechanical ignition systems is the inability to control individual cylinder timing. In a conventional mechanical ignition system, the timing is set in relation to TDC of one cylinder. Typically, the first cylinder that fires is used to physically set when the rotor of the distributor makes contact with the terminal which supplies the current to the spark plug when that piston is at TDC, or at a particular degree of timing before TDC, i.e. rotor phasing. Once the rotor is phased, all cylinders will then fire in relation to this pre-determined phasing. The timing can be further adjusted by rotating the entire distributor and shaft and with a timing light, monitoring the timing at the balancer.
In high RPM engines, it may be advantageous to have one or more cylinders firing before or after the pre-selected timing to optimize the efficiency for the conditions of each individual cylinder. For example, with the timing set at 30 degrees advance (before TDC), one cylinder which creates a higher pressure than the rest may burn more efficiently if fired at 25 degrees advance. Thus, for peak efficiency and maximum power applications, it is advantageous to be able to control individual cylinder timing. Although this may be achieved by some real-time using computer systems, these systems may be too slow for high RPM engines and may not be allowed by race sanctioning bodies and further, they do not allow the user to select and specify the individual cylinder timing.
In high performance engines, as well as all engines, there exists an optimum RPM to shift from one gear to the next. It is well known in the automotive industry to use a "shift light" to signal the driver to manually shift gears once the correct RPM has been reached for that particular gear shift. Such shift lights are typically controlled by an electronic system which monitors the tachometer and sends a signal to illuminate shift light once a particular RPM determined by a computer or a dial-type switch has been reached. In an automatic transmission, this signal can also be used to activate an automatic shifter. Typically, these gear shift systems are separate and independent of the electronic ignition timing systems and, thus, two electronic "boxes" must be placed on the car.
One attempt to combine both an ignition timing and gear shift controller is the QUICKSHOT.TM. Programmer and ProStrip Annihilator ignition system developed by Holley Performance Products. Due to the small physical size, the programmer uses a two digit or letter code to identify the parameter and then removes the code and displays the first two digits of value for that particular parameter. Thus, the user must either memorize or use a reference aids to identify the code for the parameter. However, this may become very inconvenient for the racer in the field where the level of surrounding activity can be extremely disruptive due to the limited time between runs, to refer to a reference manual or code sheets while attempting to make adjustments. Moreover, if the codes are confused and the wrong engine control parameter is inadvertently changed, misfiring, or incorrect shifting may result which can cause significant engine damage. Furthermore, due to the limited display on the programmer, approximately 1.25 inches by 1 inch, only one individual parameter code can be viewed and selected at a time. Also, this system does not provide an efficient, user-friendly method for controlling individual cylinder ignition timing.
Accordingly, an interface that allows a wide variety of engine operational parameters to be adjusted via an easy to recognize engine parameter terms on its display. In this regard, a system is needed which allows engine parameter changes to be made quickly without the need of reference materials and provide safeguards to prevent for inadvertent changes in one engine control parameter which may dampen performance or result in engine damage. Furthermore, it would be desirable to provide a programmable engine control system capable of controlling multiple functions such as gear shifting, individual cylinder timing and RPM controls in one box thereby reducing the number of electronic units needed in the car.